Electromagnetic apparatus



Feb. 12, 1924.- 1,483,682

J. A. ROSTRON ELECTROMAGNETIC APPARATUS Filed May 5. 1920 Ina/wilful"JOSEPH A R05 77? ON Patented Feb. 12, 1924.

UNITED STATES JOSEPH A. ROSTRGN, F BOSTON, MASSACHUSETTS.

ELECTROMAGNETIC APPARATUS.

Application. filed May 3, 1820.

To all whom it may 0071mm.

Be it known that I, Josnrn A. Ros'rnoN, a citizen of Great Britain,residing at Boston, in the county of Suffolk and State of Massachusetts, have invented certain new and useful Improvements inElectromagnetic Ap paratus, of which the following is a specification.

The present invention relates to buzzers,

so called, in the general class of electrd magnets and electromagneticswitches, adapted as rapid make and break contact apparatus to produce avibration making a sound or ringing a bell, and to magnets for otheruses.

The object of the invention is to provide improved electromagneticapparatus of this sort which shall be extremely simple in construction,economical to manufacture, compact, and efficient in operation.

In particular it is an object to avoid the customary U-shape of magnet,which is rela tively expensive to construct, and to do this without lossof magnetic efiiciency; also to produce an armature of inexpensive buteffective type, and to provide also for adjustments.

According to the present invention an inexpensive, straight, fiat bar ofiron is the core adapted to attract a sheet metal. armature. The sidesof the end portions of the metal core constitute pole faces for thesides of the end portions of the armature. The coil is wound about themiddle of the core. The armature is substantially parallel to the coreat a little distance therefrom, but the sides of its end portions areoffset toward the core so that the armature constitutes an iron pathfrom one end to the other of the straight core, such path being bowedout around the Winding thereon. To obtain a buzzer effect the armaturemay have a sheet metal integral extension edgewise from its middle, longenough to have necessary flexibility for vibration when clamped at theextremity. The neck leading to this clamped end may make and breakcontact with a bit of sheetmetal constituting a stationary switch memherjust beside it. A very simple and etfi cient device is thus providedthat is procurable for a small fraction of the cost prevailing forsimilar articles today. The principle may however be applied in moreexpensive and larger apparatus with correspond ing advantages.

Serial No. 378,476.

In the accompanying drawings illustrating the invention:

Figure 1 is a perspective view of one embodiment of the presentinvention showing the base in dot-and-d-ash lines and the armature incontact with the core;

Figure 2 is a section on the line 22 of Fig. 1, looking in the directionof the arrows;

Figure 3 shows the same as a bell.

The electro-magnet of the present invention comprises a fiat, straightcore 2, the sides of whose ends 4 and 6 constitute pole faces being infact a simple section cut from a length of bar iron and an energizingwinding 14 thereon. The armature 8 is preferably a stamping of thinsheet iron, set parallel therewith, the sides of whose end portions 10and 12 are adapted to contact with the sides of the pole pieces 4.- and6, respectively. The armature ends are ofiset towards the poles from thebody portion of the armature, it being ordinarily less expensive to bendsuch thin sheet metal, and less expensive to wind the coil on a straightcore. In the illustrated embodiment of the invention, the offset endsare thus shown upon the sheet metal armature, the ofisetting beingeffected by a die which blanks out the shape and then bends the ends,which may be all at one operation. The armature is a T-shaped piece,with the leg of the T constituting a flexible stem that holds thearmature proper, whose poles are at the ends of the arms of the T. Whenthe winding 14 is energized, the armature will be drawn to the coreuntil their respective ends are in contact, thus closing a good magneticcircuit. As the winding is flat on account of flat shape of the core,the armature body can fairly be close to it and substantially parallelwith it, with one side 18 of the coil lying in the bowed space 16 of thearmature, whereby a very compact structure is obtained.

In order to adapt the electro-magnet to switch purposes, the armature ismade the movable member. The core is accordingly shown as stationary,supported upon the bottom 20 of an insulating base which may be a merewooden cup with the bar iron core simply pressed in tight; althoughadditional fastening may be employed if desired such as tacks driveninto the wood. The extremity of the leg 22 of the T is fastened to thebottom 2% of a recess 26 in the side wall 28 of the base. The head ofthe T is mounted parallel to the core, so that its ends may be drawn tothe poles, the somewhat springy sheet-metal leg 2-2 of the T bend1ng topermit such movement, and flying back immediately on the weakening ofthe magnet. When the armature occupies its normal open position, itcontacts with a sheetmetal switchmember 30 which is fastened in the samerecess 26, with the leg of the armature, and with the same single screw,being insulated therefrom at Thus a current is passed through the coilof the magnet. \Vhen the armature is attracted to the core, it breakscontact with the switch member, thereby opening the magnet circuit.Thereupon the armature springs back, away from the magnet. Contactbetween the armature and the switch member may thus be rapidly made andbroken in accordance with rapid energization of the winding 14, to causethe operation of a buzzer or similar device in well known manner.Terminals 36 and 38 are conveniently made in the wooden wall 28 byscrews passing through it. Of course more elaborate contacts andadjustments can be made at will, but it is one advantage of theinvention that adjustments can be made in the simple form illustrated bymerely bending the short contact piece 30 or the armature leg 22. To usethe invention as a bell a hammer 40 may be attached to the armature anda bell 42 mounted on the base, as indicated in Figure 3. The base can bemade of any other suitable material if found more desirable than thewood mentioned.

It is intended that the patent shall cover by suitable expression in thefollowing claims whatever patentable novelty is involved in theinvention disclosed.

I claim as my invention:

1. A vibrator comprising, in combination, a casing having fixed withinit an electromagnet and one electrical contact; and an armature, securedin the casing between them and bearing the other electrical contact; themagnet core and said armature being flat metal sheets arranged withtheir broad surfaces parallel to each other; the said magnet sheet beingrelatively thick, constituting a straight bar and having the windingabout its middle; and the said armature sheet being relatively thin,elastic and flexible, and having its end portion bent around the endportion of the said winding on the magnet, to proximity with the magnetcore. for vibrating toward and from the broad side of said core.

An electric vibrator having, in combination, a section of flat bar ironcomprising a core, the sides of whose ends constitute pole faces andabout whose middle is wound an energizing coil; and a T-shaped elasticsheet iron armature, the arms of the T being parallel to said bar,overlying the coil with their ends offset from the plane of the middlepart toward the respective pole faces to co-operate closely therewithnothwithstanding the coil intervening between the straight armature andcore; a base to which the leg of the T is secured; and a terminal formake and break contact with the said leg said leg and terminal havingcontacts for make and break of an electric current.

In a vibrator, the combination of two fiat, broad strips of permeablematerial arranged with their broad surfaces parallel to each other; oneof them being relatively thick and constituting an electro-magnet core,and the other relatively thin and constituting its armature: the saidcore strip being straight and having its energizing coil wound about itsmiddle; and the said armature strip being relatively thin, elastic andflexible, and having its end portion bent around the end portion of thesaid winding to proximity with the magnet core, for vibrating toward andfrom the broad side of said core.

4. A make and break apparatus comprising in combination an electromagnetwhose core is of straight bar iron whereon is wound medially an electriccoil, the sides of the ends of the bar being exposed; an armature ofsheet metal bowed around said coil with the sides of its ends againstand parallel with the said sides of ends of the magnet; a tongueextension of the sheet metal comprising the armature, perpendicularthereto, supporting it and constituting part of the electrical circuit;and a base to which it is secured at a distance from the armature,thereby to vibrate to and from. the side of the bar.

Signed at Boston, Massachusetts, this 15th day of April, 1920.

JOSEPH A. ROSTRON.

